Molecular weight regulation in polymerization of vinylidene monomers using 4, 4&#39;-isopropylidene diphenol as regulator



United States Patent l 3,160,615 MDLECUZAR WEIGHT REGULATHGN 1N PiLYMLREZATIGN 0F VENYLEDENE MGNQ- MERS USHJG 4,4'-ESQ?RQPYLHEENE DIPHE-NOL AS REGULATQR Richard E. Delacretaz and Robert L. Waiter,Springfield, Mass., assignors to Monsanto "Company, a corporation ofDelaware No Drawing. Filed Nov. 3, 1951, Ser. No. 149,862

4 Claims.

This invention relates to the polymerization of a freeradical-polymerizable material including a polar monomer and moreparticularly relates to a method of regulating the molecular Weights ofpolymers prepared by polymerizing such a free radicfl-polymerizablematerial in the absence of an organic diluent.

The tendency of certain free radical-polymerizable materials topolymerize to very high molecular weight polymers under normalpolymerization conditions is already Well known. These very highmolecular Weight polymers have the disadvantage of being difiicultlyprocessable, i.e., unable to be processed Without the use of specialprocessing equipment except at temperatures so high as to have adetrimental effect on the strength and color of the processed polymers.

Various techniques have been proposed for regulating the molecularweights of such polymers so as to make them more easily processable.Oneof these techniques is to conduct the polymerization in an organicdiluent. This technique is effective as a means of lowering molecularWeight, but it has the disadvantages of increased cost and inconvenienceof separating the polymer from the organic diluent. Other proposedtechniques avoid the disadvantages of solvent polymerization but haveunfortunate disadvantages of their own, e.g., raising the polymerizationtemperature increases the danger of a run-away polymerization, and usinga mercaptan as a chain transfer agent contributes a very unpleasant odorto the polymers.

An object of the invention is to provide more easily processed polymersof the type prepared by polymerizing a free radical-polymerizablematerial including a polar monomer.

Another object is to provide a novel process for regulating themolecular weights of such polymers without employing an organic diluentin the polymerization reaction mixture.

These and other objects are attained by conducting the polymerizau'on ofa free radical-polymerizable material 7 Polyvinyl Chloride PART A Charge100 parts of purified vinyl chloride monomer, 150 parts of water, 0.15part of lauroyl perox de, and 0.5 part of a water-soluble acrylicacid-Z-ethylhexyl acrylate (90:10) copolymer to a suitable reactionvessel. Seal the vessel and tumble it in a constanttemperature bath atC. for 15 hours. Thepolymeric product has a specific viscosity of 0.540,measured as asolution of 0.25% of the polymer in cyclohexanone.

tion to the properties of the polymersprepared in its'presa 3,,l60,0l5Patented fiec. 8, i964 ice PART B Repeat Fart A exceptfor including 0.5part of 4,4-isopropylidene diphenol in the charge to the reactionvessel. The polymeric product has a specific viscosity of 0.380.

EXAMPLE II Styrene-Aczylonitrile Copolymer PART A Charge 70 parts ofstyrene, 30 parts of acrylonitrile, parts of Water, 0.5 part ofdi-t-butyl peroxide, and 0.03 part of a water-soluble acrylicacid-2-ethylhexyl acrylate (90:10) copolymer to a suitable reactionvsesel. Heat with agitation at C. for 4 hours and then at C. for 4hours. Strip the bead slurry of unreacted monomers, wash, and dry. Thepolymeric product has a specific viscosity of 0.200 (measured as asolution of 0.1% of the polymer in dimethylformamide).

PART B Repeat Part A except for including 0.5 part of4,4'-isopropylidene diphenol in the charge to the reaction vessel. Thepolymeric product has a specific viscosity of 0.141.

EXAMPLE HI Styrene-A crylonitrile C opolymer PART A Charge a solution of2 parts of sodium stearate in parts of Water to a suitable reactionvessel and heat to 95100 C. with agitation. Continuously add a mixtureof 80 parts of styrene and 20 parts of acrylonitnile to the heated,agitated soap solution over a period of 2 hours. During the addition ofthe monomer mixture, continuously add a separate charge consisting of asolution of 0.25 part or" potassium persulfate in 50 parts of water.After completing the addition of the monomer and catalyst charges, stripthe emulsion of unreacted monomers, coagulate, and dry. 'The polymericproduct has a specific viscosity of 0.180 (measured as a solution of0.1% of the polymer in dimethylformamide).

PART B Repeat Part A except for adding 2 parts of 4,4'-isopropylidenediphenol together with the monomer charge. The product has a specificviscosity of 0.141;

The invention is a method of regulating the molecular weights ofpolymers prepared from a free radical-polymer-izable material includinga polar monomer without enlploying an organic diluent. The molecularweight regulation is achieved by conducting the polymerization of thefree'radical-polymerizable material in the presence of a minor amount of4,4-isopropylidene diphenol.

' The amount of molecular weight regulator employed in the practice ofthe invention is in the range of 0.25%, usually 0.5-3%, based on theWeight of the free radicalpolymerizable material. 4,4'-isopropylidene'di henol is ineffective as a molecular weight regulator atconcentrations lower than 0.2%. Concentrations higher than 5% areusually undesirable,'either because the higher con-v ability to act as amolecular weight regulator at such low concentrations that substantiallyits only contribu ence is an improvement in processability.

The free radical-polymerizable materials 'which are polymerized in thepresence of the molecular Weight regue) lator of the invention arematerials including a polar monomer, i.e., a monomer which has a dipolemoment of at least 1.0 Debye unit. Particularly suitable materials are:

(1) Polar vinylidene monomers, such as acrylonitrile, methacrylonitrile,vinyl chloride, an alkyl acrylate (e.g., methyl acrylate, ethylacrylate, butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate,etc.), an alkyl methacrylate (e.g., methyl methacrylate, butylmethacrylate, etc.), and mixtures thereof,

(2) Mixtures of such polar vinylidene monomers with copolymerizablemonomers, such as dialkyl maleates, dialkyl fumarates, acrylic acid,methacrylic acid, conjugated dienes (e.g., butadiene), monovinylidenearomatic hydrocarbons (e.g., styrene, alpha-methylstyrene,alphaethylstyrene, o, m-, and p-methylstyrenes, o-, m-, andp-methyl-alpha-methyl-styrenes, p-isopropylstyrene, ar-dibutylstyrenes,vinyl naphthalene, etc.), and

(3) Mixtures of non-polar vinylidene monomers with one or morecopolymerizable polar compounds other than the polar monomers mentionedabove, such as monoor dialkyl maleates or fumarates, maleic anhydride,acrylic acid, methacrylic acid, etc.

A polar monomer should comprise at least of the .weight of the freeradical-polymerizable material. Ac-

cording to one of the preferred embodiments of the invention, the freeradical-polymenizable material consists of 10-90%, by weight of one ormore monoyinylidene aromatic hydrocarbons and 90-10% by weight ofacrylonitrile and/ or methacrylonitrile.

The polymerization of the free.radical-polymerizable material in thepresence of the molecular weight regulator of the invention is conductedin the absence of an organic diluent. Polymerization may be accomplishedby any of the mass, suspension, or emulsion polymerization techniquesconventionally employed for the polymerization of such materials,usually at temperatures in the range of -200 C. at atmospheric orsuperatmospheric pressure. The reaction mixture should contain a freeradical polymerization initiator, such as a peroxy or azo compound, andany ingredient required by the particular polymerization techniqueemployed, e.g., water, an emulsifying agent, a suspending agent, etc.Optional ingredients, such as antioxidants, plasticizers, etc., can alsobe included in the reaction mixture if desired.

A preferred embodiment of the invention is the use of the molecularweight regulators in polymerization reac tions which are conducted in anaqueous medium. Ordinarily in such reactions the weight ratio of waterto free radical-polymerizable material is in the range of 9:1 to 2:3.The emulsifying agent, when employed, can be of the anionic, cationic,or non-ionic type; the suspending agent, when employed, can be inorganicor organic.

It is within the scope of the invention to conduct the polymerization inthe presence of a preformed polymer, e.g., polybutadiene, a rubberybutadiene-styrene copolymer, or the like, to graft polymeric chains ofthe free radical-polymerization material onto the preformed polymerbackbone. The molecular weight regulator serves to shorten the chainsgrafted onto the polymer backbone as well as to lower the molecularweight of any coformed, ungrafted polymer of the freeradical-polymerizable material.

The products of the invention are polymers which contain a minor amountof chemically-combined molecular weight regulator and have lowermolecular weights than the corresponding polymers prepared in theabsence of the molecular weight regulators. Because of their lowermolecular weights, they are more easily processable and can beprocessed, e.g., extruded, molded, etc., in conventional processingequipment without requiring the use of extreme temperatures Which wouldhave a detrimental eifect on the strength and color of the products.

The invention is particularly advantageous in that it accomplishesmolecular weight regulation without the aid of organic diluents,malodorous mercaptans, or reactive materials which would have to be usedin such large amounts as to have a noticeable effect on other polymerproperties as Well as on processability.

It is obvious that many variations can be made in the products andprocesses set forth above without departing from the spirit and scope ofthis invention.

hat is claimed is:

1. In a process for polymerizing a free radical-polymerizable materialof the group consisting of (a) a polar vinylidene monomer of the groupconsisting of acrylonitrile, methacrylonitrile, vinyl chloride, an alkylacrylate, an alkyl methacrylate, and mixtures thereof, (b) mixtures ofsaid polar vinylidene monomer with a copolymerizable monomer of thegroup consisting of a dialkyl maleate, a diaikyl fumarate, acrylic acid,methacrylic acid, a conjugated diene, a monovinylidene aromatichydrocarbon, and mixtures thereof, and (0) mixtures of a non-polarvinylidene monomer with a copolymerizable polar monomer of the groupconsisting of a monoalkyl maleate, a monoalkyl fumarate, a dialkylmaleate, a dialkyl tumarate, maleic anhydride, acrylic acid, methacrylicacid, and mixtures thereof in the presence of a free radicalpolymerization initiator, the improvement which comprises conducting thepolymerization in the presence of (ll-5% of 4,4'-isopropylidenediphenol, based on the weight of the free radical-polymerizablematerial.

2. A process as in claim 1 wherein the free radicalpolymerizablematerial consists of 10-90% by weight of a monovinylidene aromatichydrocarbon and -10% by weight of acrylonitrile.

3. A process as in claim 2 wherein the free radicalpolymerizablematerial consists of 10-90% by weight of styrene and 90l0% by Weight ofacrylonitrile.

I 4. A process as in claim 1 wherein the polymerization is conducted inan aqueous medium.

References Cited in the file of this patent UNITED STATES PATENTS3,110,702 Delacrctaz Nov. 12, 1963 FOREIGN PATENTS 31,828 Great BritainApr. 6, 1960

1. IN A PROCESS FOR POLYMERIZING A FREE RADICAL-POLYERIZABLE MATERIAL OFTHE GROUP CONSISTING OF (A) A POLAR VINYLIDENE MONOMER OF THE GROUPCONSISTING OF ACRYLONITRILE, METHACRYLONITRILE, VINYL CHLORIDE, AN ALKYLACRYLATE, AN ALKYL METHACRYLATE, AND MIXTURES THEREOF, (B) MIXTURES OFSAID JPOLAR VINYLIDENE MONOMER WITH A COPOLYMERIZABLE MONOMER OF THEGROUP CONSISTING OF A DIALKYL MALEATE, A DIALKYL FUMARATE, ACRYLIC ACID,METHACRYLIC ACID, A CONJUGATED DIENE, A MONOVINYLIDENE AROMATICHYDROCARBON, AND MIXTURES THEREOF, AND (C) MIXTURES OF A NON-POLARVINYLIDENE MONOMER WITH A COPOLYMERIZABLE MONOMER OF THE GROUPCONSISTING OF A DIALKYL MALEATE, A DIALKYL FUMARATE, ACRYLIC ACID,METHACRYLIC ACID, A CONJUGATED DIENE, A MONOVINYLIDENE AROMATICHYDROCARBON, AND MIXTURES THEREOF, AND (C) MIXTURES OF A NON-POLARVINYLIDENE MONOMER WITH A COPOLYMERIZABLE POLAR MONOMER OF THE GROUPCONSISTING OF A MONOALKYL MALEATE, A MONOALKYL FUMARATE, A DIALKYLMALEATE, A DIALKYL FUMARATE, MALEIC ANHYDRIDE, ACRYLIC ACID, METHACRYLICACID, AND MIXTURES THEREOF IN THE APRESENCE OF A FREE RADICALPOLYMERIZATION INTIATOR, THE IMPROVEMENT WHICH COMPRISES CONDUCTING THEPOLYMERIZATION IN THE PRESENCE OF 0.2-5% OF 4,4''-ISOPROPYLIDENEDIPHENOL, BASED ON THE WEIGHT OF THE FREE RADICAL-POLYMERIZABLEMATERIAL.